Dynamically create text inside a file using shell script-CodePudding

I am trying to dynamically create a upstream.nginx.conf file which only holds the content of upstream block in nginx which I will include in the main nginx.conf. I am trying to write a shell script to create this based on the environment variables provided in to the docker container (nginx:stable-alpine) using wildcard fetch.

The environment variables are $STABLESERVER1=sss1.int.com $STABLESERVER2=sss2.int.com

The shell script should write the file with the content by fetching the environment variables starting with STABLES*

upstream WebPool {
   server sss1.int.com;
   server sss2.int.com;
}

With no knowledge of shell scripting, I have written so far

#! /bin/sh

printenv | grep "^STABLES" | while read line; do
   echo "server    ${line#*=};"
done > upstream.nginx.conf

I am not sure how to add "upstream {" at the top and "}" at the bottom

CodePudding user response：

Assuming I have printenv with:

$STABLESERVER1=sss1.int.com
$STABLESERVER2=sss2.int.com

I would do something like:

#!/bin/sh

# ! replace this line with your command !
readonly SERVERS=$(cat ./printEnvResult | grep "STABLES*")

# ! replace this with output file name !
readonly FILENAME="output.file"

echo -e "upstream WebPool {" >  ${FILENAME}
for i in ${SERVERS};
do
    echo -e "\tserver $(echo ${i} | cut -d'=' -f2);" >> ${FILENAME}
done
echo -e "}" >> ${FILENAME}

Output will be:

upstream WebPool {
        server sss1.int.com;
        server sss2.int.com;
}

I tested this with a file instead of printenv output.